How long do dead eggs last in the hair?
Nits(eggs) will not detach on their own because they're wrapped
around and held onto the hair shaft with a glue-like
substance. They have to be physically removed unless this
glue is dissolved somehow or the hair with the nit attached falls
off. They grow out with the hair, and those nits that are
more than a few centimeters away from the scalp are most likely
dead or have already hatched.